diff --git a/src/js.rs b/src/js.rs
index 15fc366b..e9c08a8e 100644
--- a/src/js.rs
+++ b/src/js.rs
@@ -684,7 +684,7 @@ extern "C" {
     ///
     /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/now
     #[wasm_bindgen(static_method_of = Date)]
-    pub fn now() -> Number;
+    pub fn now() -> f64;
 
     /// The toDateString() method returns the date portion of a Date object
     /// in human readable form in American English.
@@ -771,7 +771,7 @@ extern "C" {
     ///
     /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/UTC
     #[wasm_bindgen(static_method_of = Date, js_name = UTC)]
-    pub fn utc(year: Number, month: Number) -> Number;
+    pub fn utc(year: f64, month: f64) -> f64;
 
     /// The valueOf() method  returns the primitive value of
     /// a Date object.
diff --git a/tests/all/js_globals/Date.rs b/tests/all/js_globals/Date.rs
index e7021255..cdabfd9a 100644
--- a/tests/all/js_globals/Date.rs
+++ b/tests/all/js_globals/Date.rs
@@ -42,10 +42,10 @@ fn now() {
 
             extern crate wasm_bindgen;
             use wasm_bindgen::prelude::*;
-            use wasm_bindgen::js::{Date, Number};
+            use wasm_bindgen::js::Date;
 
             #[wasm_bindgen]
-            pub fn now() -> Number {
+            pub fn now() -> f64 {
                 Date::now()
             }
         "#)
@@ -360,11 +360,11 @@ fn utc() {
 
             extern crate wasm_bindgen;
             use wasm_bindgen::prelude::*;
-            use wasm_bindgen::js::{Date, Number};
+            use wasm_bindgen::js::Date;
 
             #[wasm_bindgen]
-            pub fn utc() -> Number {
-                Date::utc(Number::new(JsValue::from(2018)), Number::new(JsValue::from(6)))
+            pub fn utc() -> f64 {
+                Date::utc(2018f64, 6f64)
             }
         "#)
         .file("test.ts", r#"